Okay, that's what I thought then.
I don't think we can't use "skimp" this way in English, it fits in sentences like
Give me a hot dog, and don't skimp on the mustard.
but here I think we should use the verb "withhold." It means kind of the same thing, and it doesn't have the "slangy" quality of "skimp."
If the meaning is
Don't be stingy with your "yes" answers
then we can say
...nor withhold the "yes."
This will be in acceptable English, and the meaning will be what the original source text wants to say.